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Phase diagram of one-patch colloids forming tubes and lamellae
Zdenek Preisler1, Teun Vissers, Frank Smallenburg
1Dipartimento di Fisica, Università di Roma Sapienza, Piazzale Aldo Moro 5, 00185 Roma, Italy.
The Journal of Physical Chemistry. B
|August 2, 2013
Summary
One-patch particles form metastable tubes in the fluid phase. These tubes are always less stable than a lamellar crystal, though packed tubes can be stable at high pressures.
Area of Science:
- Physical Chemistry
- Materials Science
- Computational Physics
Background:
- One-patch particles with 30% patch coverage are known to form long, tubelike aggregates in the fluid phase.
- Understanding the thermodynamic stability of these aggregates is crucial for predicting material behavior.
Purpose of the Study:
- To numerically calculate the equilibrium phase diagram for one-patch particles with 30% patch coverage.
- To determine the stability of the disordered tube phase relative to crystalline phases.
- To identify all stable crystalline phases and the conditions under which they form.
Main Methods:
- Numerical calculation of the equilibrium phase diagram.
- Free-energy calculations to assess phase stability.
- Exploration of particle density and temperature effects on phase formation.
Main Results:
- The disordered tube phase, while forming spontaneously, is always metastable compared to a lamellar crystal.
- A crystal of infinitely long packed tubes is thermodynamically stable, but only at high pressures.
- The model's phase diagram includes four distinct stable crystals alongside the fluid phase.
- No gas-liquid critical point or liquid phase was detected.
Conclusions:
- The spontaneous formation of tubes in the fluid phase does not guarantee their thermodynamic stability.
- Lamellar crystals are favored over the disordered tube phase under typical conditions.
- High pressure is required for the formation of stable packed tube crystals.
- The phase behavior of these one-patch particles is complex, featuring multiple crystalline structures and lacking a conventional liquid phase.
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